Laminated countertops are constructed with a thin surface layer of plastic laminate, such as FORMICA.TM. brand laminate from the Formica Corporation, Cincinnati, Ohio. The laminate is generally made up of layers of colored paper impregnated with polymeric resin and pressed into sheet stock. The surface laminate is typically bonded to a wood fibre core, such as plywood, particleboard or flake board. To mount a sink in a laminated countertop, a cross-sectional hole must be cut through the laminate and core. The wood fibre core exposed by the cross-sectional cut is generally porous, so that a seal must be used to exclude water from the unlaminated, cut edge of the countertop. Typically, this is achieved by dropping a sink with an upper circumferential flange into the mounting aperture from above, and sealing the flange against the laminated countertop.
The traditional mounting for flanged drop-in sinks gives rise to a number of problems. Because the flange is raised or bevelled, it is not possible to run cleaning solution over it freely, since the cleaner would not run back into the sink but out over the countertop. Perhaps more importantly, if the seal between the sink flange and the countertop laminate deteriorates, water can leak down into the exposed porous wood fibre edge of the countertop core. The positioning of the flange above the wood fibre edge facilitates this undesirable flow. Eventually, the countertop may suffer structural failure as the wetted core first swells, then looses its structural integrity altogether. Even before the fibre core fails, however, the area beneath a leaking sink flange may become an unsanitary habitat for the proliferation of microorganisms.
Solid surface countertops, such as granite, have long provided an alternative to laminated countertops. Although advantageous, solid surface countertops were initially too expensive for the mass market. In the 1960's, E. I. du Pont de Nemours and Company developed an alumina trihydrate filled methylmethacrylate polymer solid surface countertop material, marketed under the trade-mark CORIAN.TM.. Similar polyester resin based "cast marble" synthetic products are also available, such as AVONITE.TM. (by Avonite, Inc., Belen, N. Mex)., FOUNTAINHEAD.TM. (by the Neveman Division of International Paper, Odenton, Md.) and SURELL.TM. (by Wilden Industries, Inc.). These solid surface materials generally have high temperature resistance, low thermal expansion, low water absorption (non-porous) and are hard and impact resistant. The widespread market acceptance of novel solid surface materials has led in turn to new developments in kitchen and bathroom fixtures.
Unlike laminated countertops, solid surface countertops lack a porous wettable core. As a result, a sink may be mounted to the underside of an aperture cut in a solid surface countertop, and the non-porous cross-sectional edge of the countertop left exposed without risk of damage to the countertop. To take advantage of this feature, a wide range of sinks are available that have been adapted for installation below countertop surfaces. These undermount sinks generally include an upper perimeter flange adapted to seal against the underside of a solid surface countertop.
At least in part because of the problems inherent in the typical top-mounting of drop-in sinks, undermount sinks have gained widespread acceptance for use with solid surface countertops. Unfortunately, solid surface countertops remain significantly more expensive than laminated countertops. As yet, however, no workable marriage exists between the economic advantages of laminated countertops and the aesthetic and functional advantages of undermount sinks.